1. Field of the Invention
The present invention relates to an exhaust air cleaning apparatus for cleaning or purifying exhaust air containing by-products generated in an image forming apparatus during image formation, and, the image forming apparatus for appropriately cleaning exhaust air containing by-products generated during image formation.
2. Description of Related Art
It is conventionally known that image forming apparatuses such as a copier, a printer, a facsimile machine, or a combined machine including multiple functions thereof, generate various by-products during image formation. The by-products are for example odor, VOC (Volatile Organic Compounds), low-molecular siloxane, and powder dust (toner, paper dust, etc.). In general, an image forming apparatus is configured to suck by-products from the site of generation thereof and collect the sucked by-products with a filter based on a fixed standard to prevent discharge of the by-products out of the apparatus.
Such an image forming apparatus configured to collect the by-products is for example disclosed in Japanese patent application publication No. 10-161491 (1998). This publication discloses an image forming apparatus provided, on its rear side, with an exhaust fan for exhausting air from the apparatus and an external exhaust duct including a filter to collect by-products. The external exhaust duct is provided protruding from the rear side of a main unit of the apparatus. The apparatus is further provided, in a place of the rear side other than the external exhaust duct, with an exhaust port for discharging the air containing no by-products in order to cool the inside of the main unit. Even if the thus configured image forming apparatus is installed in a place so that the rear side closely contacts with a wall of the installation place, the cooling exhaust port is not closed by the wall because of the external exhaust duct is provided on the rear side. This enables smooth exhaust of the cooling air. Since the external exhaust duct is detachably attached to the rear side of the main unit, the apparatus with the exhaust duct detached can be carried in a room whose doorway is narrow and others. This provides improved distribution easiness.
Further, Japanese patent application publication No. 2004-354663 discloses an image forming apparatus provided with a plurality of exhaust ducts each including an exhaust fan and a suction filter and being configured to individually such by-products from the site of generation thereof, and a communication duct in which exhaust air streams from the exhaust ducts enter together. In the communication duct, there are provided an ozone filter and an air pressure meter for measuring air pressure at an upstream position from the ozone filter. Based on measured values by the air pressure meter, the exhaust fans in the exhaust ducts upstream of the communication duct are controlled to adjust the air pressure in the communication duct to fall below a predetermined value. This enables suppressing deterioration of exhaust efficiency without applying excessive load to the exhaust fans.
Meanwhile, some users of the image forming apparatuses demand for further cleaning or purifying of even exhaust air that satisfies standards by passing through the filter. Therefore, it is conceivable to attach an exhaust air cleaning apparatus such as the external exhaust duct of the publication No. 2004-354663 including the cleaning filter for further cleaning exhaust air to the exhaust port of the image forming apparatus already installed. However, when the exhaust air cleaning apparatus is connected to the exhaust port, it is necessary to appropriately control the pressure at a position upstream of the cleaning filter in the exhaust air cleaning apparatus. When the pressure at the above position is too high, the exhaust air from the exhaust port of the image forming apparatus is not allowed to appropriately pass through the cleaning filter of the exhaust air cleaning apparatus. Thus, the inside of the image forming apparatus could not be appropriately cooled, which may cause excessive temperature increase in the image forming apparatus. This is because the exhaust air that could not pass through the cleaning filter of the exhaust air cleaning apparatus is likely to leak through a connection part or connection part between the exhaust port of the image forming apparatus and the exhaust air cleaning apparatus and others.
It is therefore conceivable, as disclosed in the publication No. 2004-354663, to provide the air pressure meter on an upstream side of the cleaning filter in the exhaust air cleaning apparatus to continuously keep the pressure at the position of the air pressure meter to be the predetermined value or less. However, when the pressure on the upstream side of the cleaning filter in the exhaust air cleaning apparatus is too low, the inside of the image forming apparatus may be excessively cooled. Specifically, for example, there is a problem that the fixing unit for fixing a toner image by heat is excessively cooled, resulting in toner fixing failures.
The above problems also occur in an image forming apparatus including two or more fans arranged in series on an exhaust path for exhausting air from the apparatus. Specifically, when the pressure between the fans placed in series on the exhaust path is not appropriate, resulting in inappropriate exhaust, the following disadvantages are caused. The internal temperature of the apparatus may excessively rise. The exhaust air before passing through the cleaning filter may leak out of the apparatus. In addition, the fixing unit may be excessively cooled.
The present invention has been made to solve the above problems of the aforementioned conventional arts and has a purpose to provide an exhaust air cleaning apparatus and an image forming apparatus capable of suppressing adverse influences on devices or units for image formation and quality deterioration of an image to be formed and also appropriately collecting by-products generated during image formation.